A system for editing sky images using an image database

Synthetic images of outdoor scenes generated by computer graphics usually contain the sky as background. The appearance of the sky plays an important role in enhancing the reality of scenes. In this paper, we propose an intuitive and interactive system for synthesizing sky images that can reflect the user's intention. Our system consists of two steps. The first step is a sky generation step. The luminance distribution and colors of the sky are generated using our intuitive user interface. The second step is a cloud composition step. We have prepared a database of photographs of real clouds. Our system searches the database for cloud photographs that are suitable for the synthesized sky. The user selects the clouds in the search results and they are composited into the sky image. By using our system, the user can easily generate desired sky images.